1. Field of the Invention
The present invention is related to a digital IF demodulator, and more specifically to a digital IF demodulator for processing television signals.
2. Background Art
Various analog IF demodulators are used to process television signals. These analog approaches require very accurate filter implementations that often require expensive and time consuming tuning of individual units. To properly recover the video, the shape of the Nyquist filter in the receiver needs to be defined accurately, and the tuner needs to accurately center the picture carrier exactly in the middle of the Nyquist slope of the IF filter, which requires high precision phase lock loops in the tuner. Conventionally, this required separate preprocessing filters for NTSC analog television signals and digital television signals, as well as a separate IF demodulator for the NTSC analog signal. Thus, what is needed is a digital IF demodulator that lessens the filtering requirements on the RF tuner.
It is also desirable to integrate the IF demodulator onto a single low cost silicon substrate fabricated with the low cost Complementary Metal Oxide Semiconductor (CMOS) process. Such integration reduces part count, cost, and size. Complete integration into a single, low cost substrate has been difficult to achieve because the limitations of the designed circuitry often call for external components. Such external circuitry typically requires components having large values of capacitance and inductance that do not facilitate integration into a single substrate.
Thus, what is needed is a digital IF demodulator that may be completely integrated onto a single silicon substrate. Such a demodulator would minimize or eliminate external circuitry, and allow efficient and economical integration and fabrication on a single silicon substrate.